Vom Willebrand factor (VWF), a plasma protein necessary for platelet-dependent primary hemostasis, is synthesized by vascular endothelial cells in vivo and in vitro. Genetically determined quantitative or qualitative abnormalities in VWF (collectively termed von Willebrand's disease - VWD) are common causes of bleeding diatheses. The molecular basis of these disorders remains largely unexplored. I hypothesize that a variety of specific defects in endothelial cell biosynthetic and secretory events may constitute the basic lesions in many forms of von Willebrand disease. I therefore propose to study VWF biosynthesis, storage, and secretion in normal and VWD-derived cultured vascular endothelium using the techniques of molecular biology, protein biochemistry, cell fractionation, and ultrastructural analysis. I hope to define the precise intracellular steps of VWF biosynthesis and processing in both normal and VWD-derived cells and by comparison of these to elucidate the molecular basis of von Willebrand's disease. In addition to its role in normal hemostasis, VWF has also been implicated in the pathophysiology of a number of vascular disease processes including atherosclerosis and thrombosis. I hypothesize that acquired alterations in endothelial biosynthesis or secretion of VWF, in response to local or systemic mediators, may be of central importance in these conditions. I therefore propose to study aspects of VWF biosynthesis by cultured endothelial cells maintained in the presence of a number of biologic agents. Special emphasis will be placed on certain inflammatory and immune mediators which have been previously shown to exert profound influences on human endothelium in culture and which may be important in the pathogenesis of a number of vascular disease entities.